Tutorial: Create a HTTP handler

Let's start by using the editor to write an API endpoint that responds to a browser HTTP request.

1. To create a new HTTP endpoint, we first bring up the omnibox, by clicking anywhere on the screen, pressing Cmd-k/Ctrl-k, or pressing the plus next to HTTP on the sidebar.

2. Enter the HTTP method GET, and the HTTP route /math.

3. You can now write any code in the blank – this is the return value of the API endpoint that you've just created. To start with, let's just return 4.

4. Click the handler's menu (☰) in the upper right and select "open in new tab", to see your API endpoint running in production.

5. Go back to Darklang to edit your code. Add + 5 to the end of the code and leave your cursor in line.

• The 9 below the handler shows you the return value for the handler.

• The 5 on the left shows you the result of the expression where the cursor currently is (in this case, 5). This isn't very useful when it's an integer, but if it's a variable it will show you the result of the variable.

6. Hover your mouse over the white dots on the left. Each dot is a "trace", representing a single request to your handler. Traces are fundamental to coding in Darklang, and we'll come back to them later.

Congratulations! You've now created (and deployed) a HTTP endpoint on Darklang.